Four-wire (Kelvin) connection
For the highest accuracy when measuring low values of resistance,
we recommend a 4-wire measurement (Kelvin lead connection). For
this measurement, connect one pair of test leads from the two current
source connectors (marked SOURCE) to the unknown resistance.
Connected a second pair of test leads from the voltmeter input
terminals (+ and - jacks) to the unknown. Now current from the
current source does not flow through the voltmeter leads, so the
resistance of the test leads is not included in the measurement.
The resolution of the reading varies with the range and with the
reading rate as shown in Table 1 on page 3.
DC Voltage Outputs
Two independent dc voltage outputs are available at the DCX-127
front panel. Each output may be set with 20 microvolt resolution
(approximately 20 bits equivalent) to any voltage in the ±10.5000 volt
range.
Description
DC Voltage Outputs
DCX-127 Multifunction Module User’s Guide
Page 5
Vmeas
Rw
(test lead)
Rw
Rw
Rw
(test lead)
Rx
(unknown)
Iref
Icomp
+INPUT
-INPUT
600
600
-SOURCE
Figure 2.
Simplified
diagram of
4-wire
ohmmeter
operation
